package yaml

import (

	"reflect"

	"unicode"

)

type keyList []reflect.Value

func (l keyList) Len() int      { return len(l) }

func (l keyList) Swap(i, j int) { l[i], l[j] = l[j], l[i] }

func (l keyList) Less(i, j int) bool {

	a := l[i]

	b := l[j]

	ak := a.Kind()

	bk := b.Kind()

	for (ak == reflect.Interface || ak == reflect.Ptr) && !a.IsNil() {

		a = a.Elem()

		ak = a.Kind()

	}

	for (bk == reflect.Interface || bk == reflect.Ptr) && !b.IsNil() {

		b = b.Elem()

		bk = b.Kind()

	}

	af, aok := keyFloat(a)

	bf, bok := keyFloat(b)

	if aok && bok {

		if af != bf {

			return af < bf

		}

		if ak != bk {

			return ak < bk

		}

		return numLess(a, b)

	}

	if ak != reflect.String || bk != reflect.String {

		return ak < bk

	}

	ar, br := []rune(a.String()), []rune(b.String())

	for i := 0; i < len(ar) && i < len(br); i++ {

		if ar[i] == br[i] {

			continue

		}

		al := unicode.IsLetter(ar[i])

		bl := unicode.IsLetter(br[i])

		if al && bl {

			return ar[i] < br[i]

		}

		if al || bl {

			return bl

		}

		var ai, bi int

		var an, bn int64

		if ar[i] == '0' || br[i] == '0' {

			for j := i-1; j >= 0 && unicode.IsDigit(ar[j]); j-- {

				if ar[j] != '0' {

					an = 1

					bn = 1

					break

				}

			}

		}

		for ai = i; ai < len(ar) && unicode.IsDigit(ar[ai]); ai++ {

			an = an*10 + int64(ar[ai]-'0')

		}

		for bi = i; bi < len(br) && unicode.IsDigit(br[bi]); bi++ {

			bn = bn*10 + int64(br[bi]-'0')

		}

		if an != bn {

			return an < bn

		}

		if ai != bi {

			return ai < bi

		}

		return ar[i] < br[i]

	}

	return len(ar) < len(br)

}

// keyFloat returns a float value for v if it is a number/bool

// and whether it is a number/bool or not.

func keyFloat(v reflect.Value) (f float64, ok bool) {

	switch v.Kind() {

	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:

		return float64(v.Int()), true

	case reflect.Float32, reflect.Float64:

		return v.Float(), true

	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:

		return float64(v.Uint()), true

	case reflect.Bool:

		if v.Bool() {

			return 1, true

		}

		return 0, true

	}

	return 0, false

}

// numLess returns whether a < b.

// a and b must necessarily have the same kind.

func numLess(a, b reflect.Value) bool {

	switch a.Kind() {

	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:

		return a.Int() < b.Int()

	case reflect.Float32, reflect.Float64:

		return a.Float() < b.Float()

	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:

		return a.Uint() < b.Uint()

	case reflect.Bool:

		return !a.Bool() && b.Bool()

	}

	panic("not a number")

}